The paper shows that the dependence of the number of the extreme resolved line on the electron density obtained for the Balmer series (Kurochka, 1967) considering the broadening action of the electrons, remains true for the Lyman and Paschen series as well. For these series a formula which gives the dependence of the number of the extreme resolved line on the velocity of hydrogen atoms when the lines are broadened by the Doppler effect, has been derived.The paper also gives the dependence of the number of the extreme resolved line on the electron density at different values of atom velocities for the joint action of the Stark and Doppler effects. The electron density in certain chromospheric flares, prominences, and in the chromosphere has also been determined.